Libellés

vendredi 30 mars 2018

126- The soil -5- About the importance of fungi

THE
SOIL – ABOUT THE IMPORTANCE OF FUNGI

How
fungi helped create life as we know it

Under
the title "How fungi helped create life as we know it", a team of
scientists from the University of Leeds (United Kingdom) published in December
2017, an exciting article on the role of fungi in the development of our
planet.

I
found this article on a Facebook page that I like very much and from time to
time I use publications, "Sols Vivant Québec" (Living Soils Quebec).
I recommend that anyone interested in these issues follow it. The publications
are usually in French or English.

“Today our world is visually dominated
by animals and plants, but this world would not have been possible without
fungi, say University of Leeds scientists.

Researchers have carried out
experiments where plants and fungi are grown in atmospheres resembling the
ancient Earth and, by incorporating their results into computer models, have
shown that fungi were essential in the creation of an oxygen-rich atmosphere.

Humans and other mammals require
high levels of oxygen to function, and it is generally thought that the planet
developed an oxygen-rich atmosphere around 500 to 400 million years ago, as
carbon dioxide was gradually photosynthesised by the first land plants.

The research team: Dr. Katie Field
from the Centre for Plant Sciences, Dr. Sarah Batterman from the School of
Geography and Dr. Benjamin Mills from the School of Earth and Environment, show
that fungi played a critical part in establishing the breathable atmosphere on
Earth by "mining" the nutrient phosphorus from rocks and transferring
it to plants to power photosynthesis.

The new research shows that the
amount of phosphorus transferred could have been very large under the ancient
atmospheric conditions, and, using an "Earth system" computer model,
the team show that fungi had the power to dramatically alter the ancient
atmosphere.

Vital relationship

While many modern plants can gather
their nutrients direct from soils through their roots, the earliest forms of
plant life faced an entirely different climate, did not have roots and were
non-vascular, meaning they could not hold water or move it around their system.

The "soil" they came into
contact with was a mineral product lacking in organic matter, which is why
their relationships with fungi were so important.

Fungi have the ability to extract
minerals from the rocks they grow on through a process known as biological
weathering. The fungi express organic acids which help to dissolve the rocks
and mineral grains they grow across.

By extracting these minerals and
passing them on to plants to aid the plants' growth, the fungi in return
received the carbon the plants produced as they photosynthesised carbon dioxide
from the atmosphere.

Gas exchange

Lab experiments undertaken by the
Leeds team have shown that different ancient fungi, which still exist today,
conducted these exchanges at different rates, which influenced the varied speeds
at which plants produced oxygen.

In turn this affected the speed at
which the atmosphere changed from being much more rich in carbon dioxide to
becoming similar to the air we breathe today.

Dr. Field said: "We used a
computer model to simulate what might have happened to the climate throughout
the Palaeozoic era if the different types of early plant-fungal symbioses were
included in the global phosphorus and carbon cycles.

"We found the effect was
potentially dramatic, with the differences in plant-fungal carbon-for-nutrient
exchange greatly altering Earth's climate through plant-powered drawdown of CO2
for photosynthesis, substantially changing the timing of the rise of oxygen in
the atmosphere."

Dr. Mills said:
"Photosynthesis by land plants is ultimately responsible for about half of
the oxygen generation on Earth, and requires phosphorus, but we currently have
a poor understanding of how the global supply of this nutrient to plants works.

"The results of including data
on fungal interactions present a significant advance in our understanding of
the Earth's early development. Our work clearly shows the importance of fungi
in the creation of an oxygenated atmosphere."

Dr. Batterman added: "Our
study shows tiny organisms such as fungi can have major effects on the global
environment. Our critical finding was that the nature of the relationship
between fungi and plants could have transformed the atmospheric carbon dioxide,
oxygen and ultimately global climate in very different ways, depending on the
type of fungi present."

The full paper, "Nutrient
acquisition by symbiotic fungi governs Palaeozoic climate transition," is
published in Philosophical Transactions of the Royal Society B.

Our
farming practices have very direct consequences for their lives and their
actions.

They
must continue to evolve and take into account, each day greater, their
environmental consequences.

We
can talk about tillage, which acts directly on soils life and on the
biodiversity they shelter. All production techniques aimed at reducing plowing
are favorable. And whatever some people think, the use of herbicides is not at
all an ecological nonsense. It is almost always preferable to use an adjusted
dose of a judiciously placed herbicide, rather than systematic plowing that is
sometimes extremely degrading.

We
can also talk about chemical fertilizers, which can act against soils. But we
must not forget that certain natural fertilizers, such as liquid or fresh
manure, also have detrimental effects. Again, it is not the fertilization
itself that is problematic, it is usually the dosage and periodicity of inputs
that can cause environmental damage. As almost always, it's a question of
balance.

Finally,
we can talk about pesticides, whose excessive concentration also affects the
life of soils. It should be noted here that the worst pesticides are not only
synthetic pesticides. I mean that the
way pesticides are produced has no relation with their dangerousness to the
life of soils. It is their persistence, their slowness to decomposition,
and of course their direct toxicity, which will have an undesirable effect.
Some synthetic pesticides are harmful, but also some pesticides authorized in
organic farming. Thus the worst pesticide in relation to life of soils is a
fungicide very widely used in organic, as in conventional farming, copper,
which does not break down and accumulates inexorably.

Our soils are the basis of our
present and especially of our food future. We must all be aware of their
importance and especially their fragility.

But
let's stop placing everything on the ideological plan. Organic is not an end in
itself. This is one of the ways that will allow preservation and even
restoration of degraded soils. But it is not the only way. We can talk about
conservation agriculture and integrated production.

Agroecology,
as it is currently being developed in France thanks to an ambitious political
and societal project, can reconcile in a common objective, most forms of
agriculture.